The present invention relates to a one dimensional length measuring device, which is easy to operate, and in particular, to an elevation measuring device, and a multidimensional coordinate measuring device.
Such measuring devices are used for measuring the dimensions, the three-dimensional shape and similar of an object. Thus, it is required, for example, when producing mechanical components to test the fabrication precision of a work piece between various fabrication steps. Thus, in a particular case, many single measurements or even a point by point measurement of entire surface portions has to be performed. The duration and the complexity of a measurement can be high, in particular, when entire batches of work pieces have to be tested.
From DE 102 15 188 B4, a digital elevation measuring device with a measurement column is known, at which a measurement slide is supported, so it can be adjusted in elevation, and which supports a measurement head with a scan element for scanning a test specimen. For vertical positioning of the measuring head, an electric motor is disposed in the base of the measuring column, which drives a pulley roller with a constant friction moment through a friction clutch, wherein a drive belt, which is connected to the measuring slide, is provided over said pulley roller. A handle is mounted to the measuring slide, in order to be able to position the measuring slide also by hand when required.
During operation, the measuring column is placed onto a stable measuring plate, on which an operator positions the test specimen to be measured in a manner suitable for the measuring function to be performed respectively. When, for example, an upper surface is to be measured, the test specimen is disposed below the measuring head. Thereafter, the operator actuates the associated measuring function key at a computer, for example, “scan surface from above”, in order to start said measuring function. The motor drives the measurement slides against the point to be measured, and loads the scan element with a constant measuring force through the friction clutch. The elevation coordinate of the measurement point is measured and displayed relative to the surface of the measuring plate, which serves as a reference.
The elevation measuring device has proven to be useful in practical applications. It enables an operator to perform various measuring functions in a comparatively simple manner, for example, measuring a surface, bore hole or shaft, from above or from below. The measuring function is selected by a simple key stroke or through a selection menu on the computer. For this purpose, however, the operator has to briefly look away from the work piece, which disturbs the workflow.
In another type of elevation measuring devices, the scan element is moved onto the surface to be measured by a mechanical turning wheel or by another mechanical or electronic control organ, until the scan element contacts said surface. The scanning is detected by a contact sensor, and subsequently, the measurement value is taken and displayed. An example for an elevation measuring device with a contact signal sensor and associated processing logic can be derived from DE 35 41 043 A1.
Through the contact signal sensor, the execution of a measurement is facilitated, however, the complexity of the elevation measuring device is increased. Furthermore, a fine positioning of the scan head is not easy with the control organ without sufficient practice, and it is perceived as complicated, when it has to be performed with mechanical control elements, for example, a hand crank or a turning wheel. In DE 35 410 43 A1, for this purpose, for example, an additional turning button is provided besides the turning wheel, wherein said turning button facilitates a highly geared down driven movement of the scan element. Such a fine positioning substantially extends the measurement time. Furthermore, certain measuring functions, for example, the measurement of a shaft or of a bore hole, cannot be performed with said type of elevation measuring device, or they cannot be performed in a simple manner.
U.S. 2004/0103548 A1 describes a similar elevation measuring device with a slide, which can be manually positioned in vertical direction by a hand crank, wherein said slide supports a scan head, and with a measurement- and display system, which detects a pressure force imparted by the scan head onto the work piece and detects the position of the scan head. During a measurement, an operator uses the hand crank in order to bring the scan head in contact with the work piece, and in order to impart a controlled pressure force onto said work piece. The strength, direction and duration of the pressure force is detected by the measurement system and displayed on a display. When the pressure force comprises a predetermined minimum strength and a rather short duration, the measurement value, which indicates the position of the scan head, is taken and displayed on the display. When the pressure force is maintained over a longer period of time, the measurement system automatically switches into an operating mode for measuring a shaft or borehole. The operator can then control the strength of the pressure force by the crank and he can scan a portion of the shaft or bore hole in order to determine, for example, an upper or lower reversal point. A position sensor or a pressure- or force sensor is used for switching the operating mode.
From practical applications, also coordinate measuring devices are known, in which the measurement head can be moved translatorically in two or three directions in space, or where it can even be pivotable about one or plural axes, see for example DE 196 41 720 C2 with further references. In order to perform measurements, mostly CNC (computer numerical control) control systems are used, which makes the devices expensive, and requires substantial knowledge and experience on the side of the operator for applications.